1. Technical Field
The present invention relates to a system supporting multimode wireless terminals and services and, in particular, to an apparatus and method for extending the utilization time of a multimode wireless terminal by reducing power consumption.
2. Related Art
A multimode wireless system is a system which provides multimode terminals with various communication services, such as voice and data services, through different communication networks when the services are required.
In order to implement multimode wireless communication, a terminal must be able to associate with more than two systems that are interoperable. For example, the wireless Internet system and the mobile communication system interoperate with each other to provide a mobile terminal with a shared service. By associating more than two different systems, roaming service is supported and a reasonable payment can be determined, whereby the subscriber can select a system suitable for his or her communication behavior, and it is possible to manage the wireless spectrum efficiently.
The multimode communication service can be implemented with a multimode terminal equipped with a plurality of wireless modems and communication protocols identical to the wireless systems to be associated with. That is, the multimode terminal should have more than two wireless modems and communication protocols. For example, in order for the mobile terminal to access a wireless local area network (WLAN) and a mobile communication system, it should have modems and protocols for both the WLAN and the mobile communication system. Accordingly, a multimode terminal is spatially limited compared to a single mode terminal. Also, since the multimode terminal should communicate, occasionally or constantly, with the multiple wireless systems, its power consumption is likely to be greater than that of the single mode terminal, resulting in the requirement for a power saving scheme.
Studies are being actively conducted to reduce the power consumption of the mobile terminal. However, most of the power-saving methods have been researched without consideration of multimode operations.
In order to reduce the power consumption of the multimode terminal, one could consider using low power consumption devices, such as a wireless modem chip, a high frequency power amplifier, a CPU, etc., that operate with low power or minimal power consumption of the terminal using the power management regulations that are supported by respective wireless communication standards related to the multimode wireless terminal.
In the former method, the power-saving effect wholly depends on the devices with which the terminal is equipped in that power consumption can be reduced as the design technologies of the devices are developed. Accordingly, this method is efficient to reduce the power consumption in voice or user data communication. However, it is limited in its ability to control power consumption in a terminal caused by high level operations, such as determinations of communication times and attempts.
The latter uses power control schemes of the wireless communication standards embedded in the respective modems of the multimode terminal. That is, most of the wireless communication standards specify the power saving schemes, and their procedures in the terminal have the limitation of power capacity, and these schemes are used for reducing power consumption in the terminal. For example, in the IEEE 802.11 standard, the wireless terminal periodically checks the packets transmitted from the access point (AP), and partially turns off the power of the modem during the rest time so as to save power.
The latter method can overcome the limitation of the former method, i.e., the lack of upper level control. However, it is difficult to use the characteristics of a multimode wireless terminal having plural modems.
This is due to the fact that the modems of the multimode wireless terminal do not interoperate with each other, but rather work independently. That is, the modems of the multimode wireless terminal operate according to the regulations defined in the wireless communication standards associated with the respective modems.
Accordingly, each modem periodically tries to connect to the wireless network equipment (AP in WLAN) corresponding to the wireless communication standard. Actually, the multiple modems do not connect to the corresponding wireless communication networks when the terminal has data to be transmitted, but they periodically connect to the corresponding wireless communication networks to determine whether or not there is data to receive. That is, it occurs that the modems connect to the corresponding wireless communication networks even when there is no data to transmit, resulting in a waste of power. Consequently, the latter method is also limited in its ability to reduce power consumption in the terminal.